These two are Jonathan Argyll art mysteries involving detective Flavia di Stefano of Rome's Art Theft Squad.
In the first, a letter turns up offering details about one of "Giotto's" (the nicknamed thief, not the esteemed painter) earliest heists and dispatches di Stefano to Florence without delay to investigate. While Flavia is there interviewing an ailing old woman, her boyfriend, art dealer Jonathan Argyll uncovers possible leads of his own in England. When he discovers his lead, dead at the bottom of the stone stairs in his rented cottage, Argyll rightly suspects foul play, especially in this little English town where the townsfolks' mouths are tighter than drumskins. What both Argyll and di Stefano discover as the truth is a little surprising and ultimately satisfying, including a lovely tiny, overlooked da Vinci sketch that sets the world right again.
In the second, Flavia spends time in Venice investigating the Titian Committee--a political body of art specialists responsible for cataloguing and identifying the master's work. To be on the committee is a plum career appointment, so when one and then two of its members is found dead, di Stefano knows there's more to these academics than meets the eye.